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NASA will launch a sample-return mission to an asteroid in 2016,
agency officials announced today (May 25).

The mission, called Origins-Spectral Interpretation-Resource
Identification-Security-Regolith Explorer (OSIRIS-Rex) will reach
an asteroid called 1999 RQ36 in 2020. The unmanned spacecraft
will use a robotic arm to snag some samples. According to the
plan, the probe will return these bits of space rock to Earth in
2023 so scientists can study them for clues about the solar
system's origin and, possibly, how life may have begun on our
planet. [ Video:
The OSIRIS-Rex Mission to 1999 RQ36 ]

The $800 million OSIRIS-Rex will be the United States' first
asteroid sample-return effort and only the second mission in
history to retrieve samples from an asteroid. Japan's Hayabusa
spacecraft successfully returned tiny grains of the asteroid
Itokawa to Earth in June 2010. [ Infographic:
How Japan's Asteroid Mission Worked ]

Itokawa is a relatively run-of-the-mill stony asteroid. 1999
RQ36, however, appears to be packed full of carbon-based
material. If an asteroid seeded Earth with life's building blocks
long ago, as many scientists suspect, it likely looked a lot like
1999 RQ36.

"We're going for something rich in organics, which might have had
something to do with life getting started," OSIRIS-Rex principal
investigator Mike Drake, of the University of Arizona, told
reporters today. "That's the idea — time capsule, containing
probably the building blocks of life."

There's also likely another reason asteroid 1999 RQ36 has drawn
the attention of scientists: The space rock has been classified
as a potentially hazardous asteroid, since its orbit brings it
close to Earth in the year 2182. There is an extremely remote
chance (a recent study pegs it at about 1-in-1000) that the
1,900-foot-wide (579-meter) asteroid
could pose a threat to Earth.

NASA selected OSIRIS-Rex as part of its New Frontiers program,
which prioritizes low-cost science missions that explore the
solar system. OSIRIS-Rex beat out two other finalists, a
sample-return mission from the far side of the moon and a mission
to the surface of Venus.

Asteroids are bits and pieces left over from the solar system's
formation more than 4.5 billion years ago, the dregs that didn't
get swept up into the sun and planets. They therefore serve as a
sort of time capsule, containing ancient material that can tell
scientists a lot about the solar system's birth.

Researchers hope OSIRIS-Rex will help them learn more about those
long-ago days, as well the possibility that an asteroid
jump-started life on Earth. 1999 RQ36 is a good study target in
this regard; telescope observations suggest it contains large
amounts of organics, Drake said.

Pristine organics from space are hard to come by on Earth; they
get scorched during their passage through the atmosphere or
contaminated by the bountiful life on our planet. That's why it's
so important, and so exciting, to snag some samples of the stuff
from an asteroid in space, according to Drake.

"We're bringing back something that's essentially untouched by
human hands, has not seen the Earth's biota and will be a
pristine sample of what's out there," he said.

The OSIRIS-Rex probe is not NASA's only mission to an asteroid.
The space agency's Dawn spacecraft is currently closing in on
Vesta, the second-largest asteroid in the solar system, and will
arrive at the space rock later this year. But Dawn will simply
orbit Vesta, not gather samples. It will also eventually leave
Vesta and rendezvous with Ceres, the largest asteroid in the
solar system, for a similar orbiting campaign. [ Photos:
Asteroids in Deep Space ]

OSIRIS-Rex, meanwhile, will get up close and personal with
asteroid 1999 RQ36 and return samples to Earth. But the mission
has a long road ahead.

Long journey and lots of reconnaissance

OSIRIS-Rex will launch in 2016 and approach 1999 RQ36 beginning
about three years later. But it won't pluck its samples
immediately. Rather, the spacecraft will study the asteroid for
about a year, so scientists can better understand its
characteristics, choose the best sampling site and map out a good
strategy.

The need for such a prolonged observation period is one lesson
learned from the Hayabusa mission, which had to do quite a bit of
troubleshooting, Drake said.

"They did not have enough time at their target asteroid, Itokawa,
to really understand the environment they were operating in and
safely conduct proximity operations leading to sample return,"
Drake said.

After performing its reconnaissance, OSIRIS-Rex will gradually
move closer to its sampling site, and the arm will extend to
collect at least 2 ounces (60 grams) of material. The spacecraft
will never actually land on 1999 RQ36.

"We kiss the surface," Drake said.

The acquired sample will be stored in a capsule, which will
eventually land at Utah's Test and Training Range in 2023. The
capsule's design will be similar to that used by
NASA's Stardust spacecraft, which returned the world's first
comet particles from comet Wild 2 in 2006.

The OSIRIS-Rex spacecraft, meanwhile, will be redirected into a
new solar orbit, likely with enough fuel to perform another
mission in the future if NASA wishes, researchers said.

Studying the sample

Once the asteroid bits come down to Earth, researchers will study
them to learn as much as they can about the solar system's
formation and the organic molecules that asteroids may be
ferrying throughout the solar system.

But OSIRIS-Rex also has other potential benefits, researchers
said.

"The knowledge from the mission also will help us to develop
methods to better track the orbits of asteroids," said Jim Green,
director of NASA's Planetary Science Division in Washington,
D.C., in a statement.

Specifically, the mission should help scientists accurately
measure the " Yarkovsky
effect " for the first time. This phenomenon is the tiny push
the sun gives an asteroid, as it absorbs sunlight and re-emits
that energy as heat. The small push adds up over time, but it's
tough to predict in detail because asteroids' shapes,
compositions and rotations can vary so much.

If scientists hope to predict a potentially hazardous asteroid's
path, they must understand the Yarkovsky effect, researchers
said. OSIRIS-Rex should help refine 1999 RQ36's orbit, allowing
scientists to get a better handle on its trajectory and possibly
understand how to mitigate or prevent potential Earth impacts.

That could come in handy with 1999 RQ36 itself, since there's a
small chance that the space rock could threaten Earth in the year
2182.

You can follow SPACE.com senior writer Mike Wall on
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